Messages in this thread | | | Date | Sun, 4 Sep 2022 12:15:20 +0200 | Subject | Re: perf top -p broken for multithreaded processes since 5.19 #forregzbot | From | Thorsten Leemhuis <> |
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TWIMC: this mail is primarily send for documentation purposes and for regzbot, my Linux kernel regression tracking bot. These mails usually contain '#forregzbot' in the subject, to make them easy to spot and filter.
[TLDR: I'm adding this regression report to the list of tracked regressions; all text from me you find below is based on a few templates paragraphs you might have encountered already already in similar form.]
Hi, this is your Linux kernel regression tracker. CCing the regression mailing list, as it should be in the loop for all regressions, as explained here: https://www.kernel.org/doc/html/latest/admin-guide/reporting-issues.html
On 02.09.22 16:46, Tomáš Trnka wrote: > Hello, > > A bug in perf v5.19 and newer completely breaks monitoring multithreaded > processes using "perf top -p". The tool fails to start with "Failed to mmap > with 22 (Invalid argument)". It still seems to work fine on single-threaded > processes. "perf record" is also unaffected. > > I have bisected the issue to the following commit: > > commit ae4f8ae16a07896403c90305d4b9be27f657c1fc > Author: Adrian Hunter <adrian.hunter@intel.com> > Date: Tue May 24 10:54:31 2022 +0300 > > libperf evlist: Allow mixing per-thread and per-cpu mmaps > > mmap_per_evsel() will skip events that do not match the CPU, so all CPUs > can be iterated in any case. > > The issue can be easily reproduced using the following test: > > $ python - <<EOF > import time > import threading > th = threading.Thread(target=time.sleep, args=(3600,)) > th.start() > th.join() > EOF > > stracing "perf top -p $(pgrep python)" yields this: > > 145184 perf_event_open({type=PERF_TYPE_HARDWARE, size=PERF_ATTR_SIZE_VER7, config=PERF_COUNT_HW_CPU_CYCLES, sample_freq=4000, sample_type=PERF_SAMPLE_IP|PERF_SAMPLE_TID|PERF_SAMPLE_TIME|PERF_SAMPLE_PERIOD, read_format=PERF_FORMAT_ID, disabled=1, exclude_kernel=1, mmap=1, comm=1, freq=1, task=1, precise_ip=0 /* arbitrary skid */, sample_id_all=1, mmap2=1, comm_exec=1, ksymbol=1, ...}, 92061, -1, -1, PERF_FLAG_FD_CLOEXEC) = 3 > > tools/perf/perf(evsel__open_cpu+0x287) [0x4c8ad7] > > tools/perf/perf(cmd_top+0x1996) [0x439b26] > > tools/perf/perf(run_builtin+0x68) [0x4a91f8] > > tools/perf/perf(main+0x645) [0x40cad5] > 145184 perf_event_open({type=PERF_TYPE_HARDWARE, size=PERF_ATTR_SIZE_VER7, config=PERF_COUNT_HW_CPU_CYCLES, sample_freq=4000, sample_type=PERF_SAMPLE_IP|PERF_SAMPLE_TID|PERF_SAMPLE_TIME|PERF_SAMPLE_PERIOD, read_format=PERF_FORMAT_ID, disabled=1, exclude_kernel=1, mmap=1, comm=1, freq=1, task=1, precise_ip=0 /* arbitrary skid */, sample_id_all=1, mmap2=1, comm_exec=1, ksymbol=1, ...}, 104619, -1, -1, PERF_FLAG_FD_CLOEXEC) = 5 > > tools/perf/perf(evsel__open_cpu+0x287) [0x4c8ad7] > > tools/perf/perf(cmd_top+0x1996) [0x439b26] > > tools/perf/perf(run_builtin+0x68) [0x4a91f8] > > tools/perf/perf(main+0x645) [0x40cad5] > …(snip)… > 145184 ioctl(5, PERF_EVENT_IOC_SET_OUTPUT, 3) = -1 EINVAL (Invalid argument) > > tools/perf/perf(perf_evlist__mmap_ops+0x2cf) [0x5d497f] > > tools/perf/perf(evlist__mmap+0xa7) [0x4c09b7] > > perf/perf(cmd_top+0x1ccd) [0x439e5d] > > tools/perf/perf(run_builtin+0x68) [0x4a91f8] > > tools/perf/perf(main+0x645) [0x40cad5] > > Best regards, > > Tomáš > -- > Tomáš Trnka > Software for Chemistry & Materials B.V.
Thanks for the report. To be sure below issue doesn't fall through the cracks unnoticed, I'm adding it to regzbot, my Linux kernel regression tracking bot:
#regzbot introduced ae4f8ae16a07896 ^ https://bugzilla.kernel.org/show_bug.cgi?id=216441 #regzbot title perf: perf top -p broken for multithreaded processes since 5.19 #regzbot ignore-activity
This isn't a regression? This issue or a fix for it are already discussed somewhere else? It was fixed already? You want to clarify when the regression started to happen? Or point out I got the title or something else totally wrong? Then just reply -- ideally with also telling regzbot about it, as explained here: https://linux-regtracking.leemhuis.info/tracked-regression/
Reminder for developers: When fixing the issue, add 'Link:' tags pointing to the report (the mail this one replies to), as explained for in the Linux kernel's documentation; above webpage explains why this is important for tracked regressions.
Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
P.S.: As the Linux kernel's regression tracker I deal with a lot of reports and sometimes miss something important when writing mails like this. If that's the case here, don't hesitate to tell me in a public reply, it's in everyone's interest to set the public record straight.
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